£260!! to be fair i got rip off once, nearly £600 for two vac motors fitted in a Steampro

that'll never happen again!!
Do you still have the old vac? dont throw it away. Send it back to the place you bought it from and get them to check it out. They might send you a new one under warrenty then you'll have a spare.
Lamb vacs are rated to 500 hours, if your not getting that out of it (hard to tell as i dont think your machine has an hours counter??) then its either faulty or your doing something wrong i.e. not ventilating the waste tank and sucking in alot of foam << these are the two main causes. But even then, the motor should last a good couple hundred hours.